WordPress is a stunning content management system which gives the user more flexibility to manage their website. Today all most websites have social sharing account and here is some popular plugins which allows you to manage your social sharing related activities.

New Facebook Comments

Here is a good plugin for WordPress which allow you to make a Facebook comments system to your WordPress site using new Facebook Graph API 2.3.

Facebook comments makes it simple to add the Facebook comments system to your WordPress site. You can also insert the facebook comment box as a shortcode into any post, page or theme.
Download the zip file from official site of WordPress.org and unzip it, once unzipped just load it to your plugins directory (wp-content/plugins/ directory) and configure it from your settings option under admin panel

SEO Facebook Comment

SEO Facebook Comments embeds a Facebook Comment Form on your blog and also looks at each of your blog posts searching for Facebook Comments already posted. All new found comments will be added to WordPress Database.

CommentPress Core

CommentPress Core is an open source theme and plugin for WordPress that allows readers to comment paragraph-by-paragraph, line-by-line or block-by-block in the margins of a text.

Annotate, gloss, workshop, debate: with CommentPress Core you can do all of these things on a finer-grained level, turning a document into a conversation. It can be applied to a fixed document (paper/essay/book etc.) or to a running blog. Use it in combination with BuddyPress and Groupblogs to create communities around your documents.